Smoking and lung cancer are almost always considered synonymous with each other, and there is a lot of truth in that. In fact, tobacco's increased risk of developing cancer in the lungs is one of the most basic harmful effects on health known.

How does smoking cause cancer?

Cigarette smoke is laden with chemicals that act as poisons for the body. Upon inhalation, these poisonous chemicals enter the blood stream, from where they lead to various diseases, including cancer. Lung, of course, remains the most easily affected organ. Tobacco smoke carries over 7000 chemicals, of which 250 are known to be poisonous. 69 chemicals out of those 250 have cancer-causing properties. Let's take a look at the different ways smoking leads to cancer in the lungs:

Damage to DNA - The chemicals in cigarette smoke like nitrosamines, benzene, benzo(a)pyrene, nickel and arsenic, and polonium-210 are known to have carcinogenic properties. These chemicals damage the DNA of genes that help protect against cancer by either attaching themselves to the DNA or by interfering in cellular processes that help repair damaged DNA.

Weakening body's defence system - There are various ways through which chemicals in smoke lower the body's defence mechanism. For example, formaldehyde destroys the hair linings in the airways, which otherwise prevent foreign substances from reaching the lower respiratory tract. Smoke also suppresses the action of cells that prevent abnormal cell proliferation (or cancer). Cadmium in smoke inhibits the action of detoxifying proteins in the body.

Long-term exposure - Smokers expose themselves to high levels of toxins over the years. Even though cancer takes years to develop, the high levels of toxic substances in a smoker's body make it difficult to cope with their damaging effects. The damage to the lung's cells and their DNA accumulate over the years to turn those cells into a cancerous state.

Addictive nature of nicotine - Nicotine, the major component present in tobacco plants is actually addictive. When inhaled, it enters the lungs, transfers to the bloodstream, and reaches the brain within seconds. Nicotine in cigarettes and other products creates an addiction quite similar to drugs like cocaine. This makes it difficult for many habitual smokers to give up smoking even if s/he wants to. Habitual use over time increases the risk of cancer.

So, does quitting help - even for a long-term smoker?

The good news is, yes! Becoming smoke-free is the first step towards reducing the risk of cancer. It may not be easy and might require external help, but the health benefits far outweigh the damaging effects:

Carbon monoxide levels in blood reach back to normal within 12 hours of quitting.

Lung function and circulation begin to show improvement within 12 weeks of quitting.

Staying smoke-free for 10 years reduces the risk of cancer in the lung by half of that of a smoker, along with reducing risk to others cancers as well.

The life expectancy increases no matter what age a person stops smoking; however, the benefit is more if one quits earlier.

What about a person who already has a positive lung cancer diagnosis - will it help to quit now? The answer is yes, quitting smoking during treatment helps the body to respond to therapy and recover quicker, while also reducing the risk of other infections and respiratory failure. Cancer patients who quit smoking also reduce their risk of recurrent cancer or a second cancer at a later time. Better late than never!